1. Technical Field
The present invention relates to an ultrasonic probe (hereunder, referred to as a “minor axis mechanical scanning probe”) that mechanically scans a piezoelectric element group in a minor axis direction, in particular, to a minor axis mechanical scanning probe in which the piezoelectric element group is linearly reciprocated in the minor axis direction.
2. Background Art
A minor axis mechanical scanning probe, for example, electronically scans a piezoelectric element group (probe main body) in the major axis direction thereof, and mechanically scans in the minor axis direction thereof, to obtain a three dimensional image (refer to Japanese Examined Patent Publication No. Hei 7-38851, Japanese Unexamined Patent Publication No. 2003-175033, and Japanese Unexamined Patent Publication No 2006-346125).
Such a probe has been brought to practical application because for example wiring (electrical connections) and scanning circuits thereof, can be made simpler, compared for example to a matrix type probe in which piezoelectric elements are arranged in lengthwise and crosswise arrays to be electronically scanned in a two-dimensional direction.
However, in the conventional minor axis mechanical scanning probe, the piezoelectric element group is electronic linear scanned in the minor axis direction in a circular arc. Therefore, so as to follow this circular arc, the ultrasonic wave transmitting/receiving surface of the sealed container also forms a circular arc convex section in the minor axis direction. Moreover, in these conventional examples, the piezoelectric element group is a convex shape (convex-curved surface) in the major axis direction, Therefore, so as to follow this shape, the shape of the sealed container in the major axis direction also forms a convex shape. Consequently, the ultrasonic wave transmitting/receiving surface becomes a convex shape in the minor axis direction and the major axis direction, so that it is entirely convex (mountain shape).
Due to this, there has been a problem in that it is difficult to bring the entire surface of the wave transmitting/receiving surface into contact with a breast (convex section, mountain section), for example when diagnosing a mammary gland of a living body (of a female in particular) with a probe. In the case where the entire surface of the wave transmitting/receiving surface does not come into contact with a breast, attenuation of the ultrasonic waves occurs, and a normal diagnostic image of the living body cannot be obtained.
Moreover, the conventional minor axis mechanical scanning probe scans a living body in a circular arc in the minor axis direction (in the piezoelectric element length direction). Hence there has also been a problem in that lateral resolution becomes rougher when a section of the living body to be scanned is deeper.
Therefore, for example, there has been proposed by the inventor (Yasunobu Hasegawa) of the present application, a minor axis mechanical scanning probe that can be easily brought into contact with a protruding portion of a living body such as breast, and that realizes excellent lateral solution (Japanese Unexamined Patent Publication No. 2008-80093).
This proposed minor axis mechanical scanning probe, as shown in FIGS. 9A and 9B, is configured such that: a plurality of strip shaped piezoelectric elements 102a is arranged in a line in the major axis direction, which is the crosswise direction of the piezoelectric elements 102a, so as to form a flat shaped piezoelectric element group 102; the piezoelectric element group 102 is housed within a sealed container 103 filled with a liquid L that functions as an ultrasonic medium; and the piezoelectric element group 102 is mechanically scanned in the minor axis direction, which is the lengthwise direction of the piezoelectric elements 102a. 
According to such a configuration, the piezoelectric element group 102 does not rotate/oscillate in a circular arc in the minor axis direction, but linearly moves (reciprocates) in the minor axis direction. Consequently, the wave transmitting/receiving surface of the sealed container 103 does not have to be made in a convex shape as with the conventional example, and can be made into a flat surface. As a result it can be made easier to fully contact the wave transmitting/receiving surface of the sealed container 103 with a living body such as breast.
Furthermore, since the piezoelectric element group 102 linearly moves (reciprocates) in the minor axis direction, ultrasonic waves from the wave transmitting/receiving surface are irradiated in parallel onto the part to be examined. Consequently, the spacing of the ultrasonic waves is constant even in a deeper part of a living body, and thereby the lateral resolution can be improved while increasing the movement speed of the piezoelectric element group.
Moreover, in this probe, as shown in FIGS. 9A and 9B, the piezoelectric element group 102 is provided on a movable mount 110 via a base 105 and a backing member 105a, and on the surface of the piezoelectric element group 102 there is provided, via an acoustic matching layer 106a, an acoustic lens 106, thereby forming a probe main body 101.
Furthermore, the configuration is such that: on both end sides of the movable mount 110 in the major axis direction, there is provided a pair of leg sections 110a and 110b, and guide shafts 111 are inserted through the pair of leg sections 110a and 110b in the minor axis direction, and supported on side walls 103b of the sealed container 103; a rack 113, in the minor axis direction, is fixed on one of the pair of leg sections 110a and 110b; and a rotating gear (pinion) 114 with an electric motor as a drive source, is meshed with the rack 113. Moreover, the guide shafts 111 passing through in the minor axis direction are provided in the pair of the leg sections 110a and 110b formed in the major axis direction of the movable mount 110 having the piezoelectric element group 102 provided thereon. Therefore the piezoelectric element group 102 can freely reciprocate in the minor axis direction. Here, the rack 113 provided in the minor axis direction on the one leg section 110a of the movable mount 110 is meshed with the rotating gear 114 with the electric motor as a drive source, and is thereby moved (reciprocated).
However, in this proposed minor axis mechanical scanning probe (Japanese Unexamined Patent Publication No. 2008-80093), as shown in FIG. 9B, the rack 113 that meshes with the rotating gear (pinion) 114 requires a length several times that of the rotating gear 114 in order to stably and linearly move the piezoelectric element group 102 in the minor axis direction with guidance of the guide shafts 111. Consequently, before the piezoelectric element group 102 can reach both of the inner walls 103a and 103b of the sealed container 103, both end surfaces of the movable mount 110 are contacted with both of the inner walls 103a and 103b. Therefore, there is a problem in that sufficient movement stroke in the minor axis direction of the probe main body can not be ensured.
A problem to be solved by the present invention is that in order to ensure sufficient movement stroke in the minor axis direction of the probe main body, then with a movement mechanism comprising an endless belt, the probe main body is reciprocated in the minor axis direction to the fullest extent between the inner walls of the container that contains the probe main body, to thereby ensure sufficient movement stroke in the minor axis direction.